Strong polling from the Liberal Democrats in the wake of last week’s election debate has put discussion of electoral reform on the agenda: a referendum on proportional representation (PR) would surely be a key condition of entering any coalition. The conventional wisdom is that PR would lead to more or less permanent centre-left government, with Labour and the Liberal Democrats always getting enough votes between them to keep the Conservatives out of office. But is this really the case?

Well, I’m not so sure, not least because I suspect people would vote very differently in a PR general election than they do in first-past-the-post ones – you can’t just take current general election vote shares and translate them into parliamentary seats to work out what a PR parliament would look like. So why not look at a recent British election that was actually conducted based on PR – the 2009 European Parliament elections – and see what kind of House of Commons that would have produced?

Based on my very rough regional calculations, which exclude Northern Ireland for the sake of simplicity, those results, replicated in a Westminster general election would have given the Conservatives 28% of the seats, Labour 18%, UKIP and the Lib Dems 16% each, the Greens 7%, and the SNP and Plaid Cymru 3% and 1% respectively. So a Conservative-UKIP coalition would have 44% of the House of Commons, while a Labour-Liberal-Green coalition would also have 44%. If you assume that no other party would agree to work with the BNP and that the Scots and Welsh nationalists would side with the left, while the Ulster Unionists (again, not included in my calculations) sided with the right, you would still be left with two coalitions of roughly equal size.

Now, OK, there’s a flaw in my logic: European election results probably flatter UKIP while causing problems for the Europhile Lib Dems. So presumably the Lib Dems would get a higher proportion of the vote, and UKIP a lower one.

But this raises another issue: would the Liberal Democrat Party stick together if became truly competitive with the other two parties, or would it split under the weight of its internal contradictions? In a PR system I can easily imagine the Lib Dems dividing into its ‘liberal’ and ‘social democrat’ factions. Many of the more libertarian Lib Dems I have spoken admit this is a serious possibility.

That would mean ‘broad churches’ in British politics – a centre-right coalition of Conservatives, Liberals, Unionists and UKIP, and a centre-left coalition of Social Democrats, Greens, Nationalists and Labour – either of whom would stand a good chance of getting 50% of the seats in the House of Commons.

But that’s enough crystal-ball-gazing. I should also point out that I do not favour PR myself. I agree with what Madsen wrote in Freedom 101:

A democracy should enable people to change their government. It is more about throwing out who they don't want than about electing the most popular. Proportional representation makes change difficult. Elections tend to bring small adjustments in the balance between the parties, and to result in coalitions of slightly different composition.

In other words, big changes from the status quo are much more difficult in PR systems. And at a time when the UK needs to depart radically its current path, that would be a very worrying development.